Patent FR-2822315-A1 (FR)
Title: Method and device for performance-constrained optimization of the size of blocks of coded data, for use in advanced telecommunication systems
Inventor: GUEGUEN ARNAUD
IPC: H03M13/39
Filed: 2001-03-19
Abstract: The method for optimizing the size of blocks of coded data to be subjected to an iterative decoding process includes, with preliminary set maximum rate of output errors, a search among the set of block sizes (N/k) for sub-multiples of the current block size given by an integer factor (k) greater than or equal to 1, and a set of integers giving the maximum number of iterations (n(k)) which can effect the iterative decoding on a block. The sub-multiple size and the maximum number of iterations are to be compatible with the maximum rate of errors, and the average number of iterations which effects the iterative decoding on a block of sub-multiple size is to be as low as possible. The average number of iterations is determined as a function of the signal-to-noise ratio so to effect the iterative decoding for each block of a succession of blocks of sub-multiple size, and the iterations are terminated when the block of sub-multiple size verifies a predetermined reliability criterion, or when the number of iterations for the block attains the maximum number of given iterations.  The average numbers of iterations for different sizes of sub-multiples, different maximum numbers of iterations and different signal-to-noise ratios are stored in a table, and the table is updated as the iterative decoding progresses; the average numbers of iterations are obtained by interpolation on the basis of values available in the table. The search is limited to integers which are greater than a predetermined value (kmin). The maximum number of iterations for a block of current size is determined preliminary to the search compatible with the maximum decoding times, and the search is limited to the values such that the average number of iterations effecting the iterative decoding is below the maximum number of iterations. For the blocks having an initial size, an optimal size of block and a maximum number of iterations associated with that size are determined by the optimization method, and the data of a block of the initial size are coded as a sequence of sub-blocks of optimal size; the sub-blocks are decoded one by one by a succession of iterations; or the sub-blocks are decoded by effecting successively on each sub-block an iteration. A device for iterative decoding of blocks of data coded by a turbo-coder comprises means for implementing the optimization method which include means for transmitting to turbo-coder an information on the optimal size of block. A system for coding/decoding comprises a turbo-coder adapted to coding the blocks of data and a device for iterative decoding which comprises means for receiving the information on the optimal size of block and for modifying the size of at least one internal interleaver as a function of received information. A device for coding the block of data comprises means for implementing the optimization method including means for adaptively modifying the size of blocks of coded data as a function of the optimal size of block. A device for turbo- equilization of blocks of data code d by a coder and modulated comprises means for implementing the optimization method including means for transmitting to coder an information on the optimal block size.